Java ConcurrentSkipListSet headSet()用法及代碼示例

headSet(E toElement)

java.util.concurrent.ConcurrentSkipListSet.headSet()方法是Java中的內置函數，它返回此集合部分的視圖，這些元素的元素嚴格小於toElement。返回的集合受此集合支持，因此返回的集合中的更改將反映在此集合中，反之亦然。返回的集合支持該集合支持的所有可選集合操作。

用法:

public NavigableSet headSet(E toElement)

參數：該函數接受元素的單個參數，即返回集的高端點。

返回值：該函數返回一個NavigableSet，該視圖是此集合中元素嚴格小於toElement的部分的視圖。

以下示例程序旨在說明ConcurrentSkipListSet.headSet(E toElement)方法：
示例1:

// Java Program Demonstrate headSet() 
// method of ConcurrentSkipListSet */ 
import java.util.NavigableSet; 
import java.util.concurrent.ConcurrentSkipListSet; 
  
class ConcurrentSkipListSetHeadSetExample1 { 
    public static void main(String[] args) 
    { 
  
        // Initializing the set 
        ConcurrentSkipListSet<Integer> 
            set = new ConcurrentSkipListSet<Integer>(); 
  
        // Adding elements to this set 
        for (int i = 10; i <= 50; i += 10) 
            set.add(i); 
  
        // Creating a headSet object with upper limit 30 
        NavigableSet<Integer> hd_set = set.headSet(30); 
  
        // Printing the elements of the set 
        System.out.println("Contents of the set: " + set); 
  
        // Printing the elements of the headSet set 
        System.out.println("Contents of the headset"
                           + " with upper limit 30: "
                           + hd_set); 
    } 
}

輸出：

Contents of the set: [10, 20, 30, 40, 50]
Contents of the headset with upper limit 30: [10, 20]

示例2:顯示NullPointerException的程序。

// Java Program Demonstrate headSet() 
// method of ConcurrentSkipListSet */ 
import java.util.NavigableSet; 
import java.util.concurrent.ConcurrentSkipListSet; 
  
class ConcurrentSkipListSetHeadSetExample2 { 
    public static void main(String[] args) 
    { 
  
        // Initializing the set 
        ConcurrentSkipListSet<Integer> 
            set = new ConcurrentSkipListSet<Integer>(); 
  
        // Adding elements to this set 
        for (int i = 10; i <= 50; i += 10) 
            set.add(i); 
  
        // Printing the elements of the set 
        System.out.println("Contents of the set: " + set); 
  
        try { 
            // Trying to creating a headSet object with upper limit null 
            NavigableSet<Integer> hd_set = set.headSet(null); 
        } 
  
        catch (Exception e) { 
            System.out.println("Exception: " + e); 
        } 
        // Printing the elements of the headSet set 
        // System.out.println("Contents of the headset" 
+" with upper limit 30: "+ hd_set); 
    } 
}

輸出：

Contents of the set: [10, 20, 30, 40, 50]
Exception: java.lang.NullPointerException

headSet(E toElement, boolean inclusive)

java.util.concurrent.ConcurrentSkipListSet.headSet()方法是Java中的內置函數，該函數返回該集合中元素小於(或等於，如果包含，則為true)toElement的部分的視圖。返回的集合受此集合支持，因此返回的集合中的更改將反映在此集合中，反之亦然。返回的集合支持該集合支持的所有可選集合操作。

用法:

public NavigableSet headSet(E toElement,
                      boolean inclusive)

參數：該函數接受以下參數

toElement即返回集的高端點。
inclusive–如果高端端點將包含在返回的視圖中，則為true。

返回值：該函數返回一個NavigableSet，該視圖是此集合中元素小於(或等於，如果包含在內，則為true)toElement的部分的視圖。

以下示例程序旨在說明ConcurrentSkipListSet.headSet(E toElement，包含布爾值)方法：

示例3:

// Java Program Demonstrate headSet() 
// method of ConcurrentSkipListSet */ 
  
import java.util.NavigableSet; 
import java.util.concurrent.ConcurrentSkipListSet; 
  
class ConcurrentSkipListSetHeadSetExample3 { 
    public static void main(String[] args) 
    { 
  
        // Initializing the set 
        ConcurrentSkipListSet<Integer> 
            set = new ConcurrentSkipListSet<Integer>(); 
  
        // Adding elements to this set 
        for (int i = 10; i <= 50; i += 10) 
            set.add(i); 
  
        // Creating a headSet object with upper limit 30 inclusive 
        NavigableSet<Integer> hd_set = set.headSet(30, true); 
  
        // Printing the elements of the set 
        System.out.println("Contents of the set: " + set); 
  
        // Printing the elements of the headSet set 
        System.out.println("Contents of the headset"
                           + " with upper limit 30 inclusive: "
                           + hd_set); 
    } 
}

輸出：

Contents of the set: [10, 20, 30, 40, 50]
Contents of the headset with upper limit 30 inclusive: [10, 20, 30]

參考： https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentSkipListSet.html#headSet-E-

相關用法

注：本文由純淨天空篩選整理自rupesh_rao大神的英文原創作品 ConcurrentSkipListSet headSet() method in Java。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。